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Lithium oxalate (Li2C2O4) is an attractive cathode pre-lithiation additive for lithium-ion batteries (LIBs), but its application is hindered by its high decomposition potential (>4.7 V). Due to the liquid–solid synergistic effect of the NaNO2 additive and the LiNi0.83Co0.07Mn0.1O2 (NCM) cathode material, the decomposition efficiency of micro-Li2C2O4 reaches 100% at a low charge cutoff voltage of 4.3 V. Our work boosts the widespread practical application of Li2C2O4 by a simple and promising electrolyte-assisted cathode pre-lithiation strategy. [ABSTRACT FROM AUTHOR]

Increasing the average Ni content and extending the working voltage are effective approaches to enhancing the reversible capacity of Li[Ni 1−x−y Co x Mn y ]O 2 layered oxide cathode materials. However, these would cause severe structural instability and rapid capacity fade upon cycling. In order to address this issue, Al3+ modified novel progressive concentration gradient material Li[Ni 0.7 Co 0.13 Mn 0.17 ]O 2 is successfully prepared, which maximizes the average Ni content as well as the surficial and structural stability at high cut-off voltage of 4.5 V, attributing to the progressively accelerated transition metals evolution rates from core to surface of the spherical particles and the Al3+ suppressed high-voltage phase transition. Consequently, superior reversible capacity of 206.1 mA h g−1 at 0.1C and capacity retention of 95.7% after 50 cycles at 0.5C rate are obtained, providing skilful approach to obtain promising high-performance cathode materials with both high energy density and long calendar life to satisfy the growing demands of future electric vehicles. [ABSTRACT FROM AUTHOR]

• A NaNO 2 -assisted strategy is proposed for cathode prelithiation with Li 2 O 2. • Synergistic effect between the NaNO 2 and cathode is revealed. • The decomposition percentage of Li 2 O 2 is high up to 96.7% at 4.4 V. • For 1 wt% of Li 2 O 2 additive, 14.85 mAh g−1 capacity could be supplied. • NaNO 2 helps to form solid electrolyte interphase rich in Li 3 N and LiN x O y. Silicon based anodes are the most attractive candidates for high energy density lithium-ion batteries (LIBs), but their practical applications are hindered by the large initial lithium loss. Cathode prelithiation is an effective method to mitigate the active lithium loss in silicon-based LIBs. However, a cathode prelithiation method enabling suitable cutoff voltage and less residues still remains challenging. Herein, we demonstrate that soluble additive NaNO 2 in carbonate-based electrolyte could efficiently reduce the decomposition voltage of Li 2 O 2 to as low as 4.3 V. The liquid–solid synergistic effect of NaNO 2 additive and LiNi 0.83 Co 0.07 Mn 0.1 O 2 (NCM) cathode on the Li 2 O 2 decomposition is revealed, which enables the highly efficient cathode prelithiation with remarkable Li 2 O 2 decomposition efficiency of 96.7% at the acceptable cutoff voltage 4.4 V. For the addition for 1 wt% Li 2 O 2 , a capacity of 14.85 mAh/g could be supplied in the first charge. Besides, NaNO 2 could reduce the active lithium loss during the following cycles for its irreversibly decomposing into Li 3 N and LiN x O y on the anode surface. The full cell assembled with NCM(Li 2 O 2) cathode and silicon-graphite (Si-G) anode delivers 17.3% higher initial specific capacity (218.6 mAh/g) than that without Li 2 O 2 (186.4 mAh/g) at the charge cutoff voltage of 4.4 V. This work provides a novel electrolyte-assisted cathode prelithiation strategy to compensate the initial active lithium loss, which is highly compatible with the current battery fabrication process. [ABSTRACT FROM AUTHOR]